Manual on Use of Self-Propelled Modular Transporters to Remove and Replace Bridges
Appendix N Example Specification for Settlement Report for Temporary Shoring on Shallow Foundations
Settlement Report for Temporary Shoring on Shallow Foundations
The Contractor's geotechnical engineer shall calculate total long-term settlement at each temporary shoring location with allowance for deck form weight, deck self-weight, and weight of the construction equipment required to place the deck concrete. References for recommended settlement calculation methodology are given below. The calculations should be based on structural borings taken at the temporary shoring locations. The results of consolidation calculations at each temporary shoring location should be plotted on a time-settlement curve and included in the report. For high-organic-content materials (organic content greater than 20%), total settlement estimates should be based on primary consolidation and secondary compression (creep) settlements. In these cases, creep estimates must be based on coefficient of secondary compression values obtained from laboratory consolidation test results. Special attention is necessary if dewatering operations are required in the vicinity of the staging area.
The Contractor's geotechnical engineer shall propose ground improvement methods under temporary shoring bents as necessary. Options may include:
- Preload temporary shoring bents,
- Rigid construction mats, and
- Dynamic compaction.
If preloading is necessary, it shall be maintained until at least 90% of the total expected (calculated) settlement has occurred.
The Contractor's structural engineer shall set differential settlement thresholds consistent with the boundary conditions used in the continuous superstructure calculation.
The report shall include a detailed settlement monitoring plan that addresses ground movements during and after the deck pour. The plan shall set survey target locations on temporary shoring and monitoring intervals with provisions for jacking under each beam line at support locations. The Report should also include a field survey of permanent bridge supports with remedial action such as pedestal grinding or bearing shims as necessary.
References:
Duncan, J.M. and Buchignani, A.L., "An Engineering Manual for Settlement Studies," Department of Civil Engineering, University of California, Berkeley, 1976.
Cheney, R.S. and Chassie, R.G., Soils and Foundations Workshop Manual-Second Edition, FHWA HI-88-009, 1993.